linux-kernel - Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the event configurations

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Message-ID: <7be35258-f913-4111-b5da-c4173615cf18@intel.com>
Date: Fri, 11 Apr 2025 15:07:39 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <tony.luck@...el.com>,
	<peternewman@...gle.com>
CC: <corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
	<hpa@...or.com>, <paulmck@...nel.org>, <akpm@...ux-foundation.org>,
	<thuth@...hat.com>, <rostedt@...dmis.org>, <ardb@...nel.org>,
	<gregkh@...uxfoundation.org>, <daniel.sneddon@...ux.intel.com>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<maciej.wieczor-retman@...el.com>, <eranian@...gle.com>
Subject: Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the
 event configurations

Hi Babu,

On 4/3/25 5:18 PM, Babu Moger wrote:
> Users can modify the event configuration by writing to the event_filter
> interface file. The event configurations for mbm_cntr_assign mode are
> located in /sys/fs/resctrl/info/event_configs/.
> 
> Update the assignments of all groups when the event configuration is
> modified.
> 
> Example:
> $ cd /sys/fs/resctrl/
> $ echo "local_reads, local_non_temporal_writes" >
>   info/L3_MON/counter_configs/mbm_total_bytes/event_filter
> 
> $ cat info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>  local_reads, local_non_temporal_writes
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v12: New patch to modify event configurations.
> ---
>  Documentation/arch/x86/resctrl.rst     |  10 +++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 115 ++++++++++++++++++++++++-
>  2 files changed, 124 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 99f9f4b9b501..4e6feba6fb08 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -335,6 +335,16 @@ with the following files:
>  	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>  	    local_reads, local_non_temporal_writes, local_reads_slow_memory
>  
> +	The event configuration can be modified by writing to the event_filter file within
> +	the configuration directory.

Please use imperative tone.

> +	::
> +
> +	    # echo "local_reads, local_non_temporal_writes" >
> +	      /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes/event_filter
> +
> +	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes/event_filter
> +	    local_reads, local_non_temporal_writes
> +
>  "max_threshold_occupancy":
>  		Read/write file provides the largest value (in
>  		bytes) at which a previously used LLC_occupancy
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index b2122a1dd36c..7792455f0b26 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1926,6 +1926,118 @@ static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq,
>  	return 0;
>  }
>  

Could you please add comments to these new functions to explain what they do?

> +static int resctrl_group_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
> +				enum resctrl_event_id evtid, u32 evt_cfg)
> +{
> +	struct rdt_mon_domain *d;
> +	int cntr_id, ret;
> +
> +	list_for_each_entry(d, &r->mon_domains, hdr.list) {
> +		cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
> +		if (cntr_id >= 0 && d->cntr_cfg[cntr_id].evt_cfg != evt_cfg) {
> +			d->cntr_cfg[cntr_id].evt_cfg = evt_cfg;
> +			ret = resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
> +						       rdtgrp->closid, cntr_id, evt_cfg, true);
> +			if (ret) {
> +				rdt_last_cmd_printf("Assign failed event %d domain %d group %s\n",
> +						    evtid, d->hdr.id, rdtgrp->kn->name);

Please provide the actual event name to user space. The event IDs are not visible to
user space.

Reinette